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Subject: Re: stanford benchmark/usenix
To: curt@emergent.com (Curt Mayer)
Date: Tue, 23 Jan 96 10:50:52 MET
From: Greg Lehey <lehey.pad@sni.de>
In-Reply-To: <199601221935.LAA19317@bluewhale.emergent.com>; from "Curt Mayer" at Jan 22, 96 11:35 am
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> 
> 
> > I had thought of a part of the system startup that checks the
> > processor type and puts in the correct hard links (symlinks are slower)
> > before any program gets started.  It would probably be a good idea to have
> > an emergency program which reinstated the generic libraries, too.
> > Greg
> 
> just a nit. symlinks are not that much slower, since the 4.4 source base
> there has been no i/o associated with a symlink.
> 
> stat-ing file
> Mon Jan 22 11:28:50 PST 1996
> Mon Jan 22 11:28:56 PST 1996
> stat-ing link
> Mon Jan 22 11:28:56 PST 1996
> Mon Jan 22 11:29:04 PST 1996
> 
> in between timestamps are 50000 calls to stat. as you can see, the incremental
> cost of hardlinks to symlinks is about 30%. another way of looking at it is
> that stat-ing a link takes about 120 microseconds, and stat-ing a symlink
> takes about 160 microseconds on a 486 dx2-80. hardly time for a disk i/o,
> or even a cache reference.

How many different links did you access?  OK, I can see that there's a
good chance of the links to the libraries being cached, but whichever
way you look at it, a symlink is still slower.  What's the advantage?

Oops, here comes another religious war...

Greg